Store variables in flash at compile time

[y009]

Hello I am using I am NRF SDK version 1.8.0 and nrf-zephyr v2.7.0-ncs1 (If a soultion exists on newer a rev, willing to upgrade now, otherwise it will happen some time in the future)
and I am looking for a good way to store factory settings on nrf9160 devices. 

I figured I'd make a separate storage partition that would be read only to the application and would be populated at compile time. 

I did find this support post:
How to store constant variables at specific address during compile time

Though the post is 6 years old now, and I'm wondering if there is perhaps a better way to do this using using ncs and wests tools
(should direct this more towards zephyr dev community?)

[Priyanka]

Hi Henry,

The post that you mentioned was for baremetal and with softdevice. With the nRF Connect SDK, you can create a new partition accessible for the application. I guess you need to give the partition data in yml file. You need to use partition manager pm_static.yml to configure what you wish. You can refer this documentation as a starting point.

Best Regards,

Priyanka

[y009]

Sorry for the late reply (probably shouldnt have asked before going on vacation).

I looked the PM before a little bit, also, and hopefully made it clear to myself.
To check:
By default the $BUILD_DIR/partitions.yml for nrf9160 has EMPTY_0, -1 and -2, which look like prime real-estate for me.

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
EMPTY_1:
  address: 0xfe000
  end_address: 0x100000
  placement:
    after:
    - littlefs_storage
  region: flash_primary
  size: 0x2000
EMPTY_2:
  address: 0xf0000
  end_address: 0xf8000
  placement:
    after:
    - mcuboot_secondary
  region: flash_primary
  size: 0x8000
app:
  address: 0x20200
  end_address: 0x80000
  region: flash_primary
  size: 0x5fe00
littlefs_storage:
  address: 0xf8000
  end_address: 0xfe000
  placement:
    align:
      start: 0x8000
    before:
    - end
  region: flash_primary
  size: 0x6000
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0x10000
  end_address: 0x10200
  placement:
    align:
      start: 0x8000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0x10000
  end_address: 0x80000
  orig_span: &id001
  - mcuboot_pad
  - spm
  - app
  region: flash_primary
  sharers: 0x1
  size: 0x70000
  span: *id001
mcuboot_primary_app:
  address: 0x10200
  end_address: 0x80000
  orig_span: &id002
  - app
  - spm
  region: flash_primary
  size: 0x6fe00
  span: *id002
mcuboot_secondary:
  address: 0x80000
  end_address: 0xf0000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x8000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x70000
nrf_modem_lib_ctrl:
  address: 0x20010000
  end_address: 0x200104e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - spm_sram
    - start
  region: sram_primary
  size: 0x4e8
nrf_modem_lib_rx:
  address: 0x200124e8
  end_address: 0x200144e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_tx
  region: sram_primary
  size: 0x2000
nrf_modem_lib_sram:
  address: 0x20010000
  end_address: 0x200144e8
  orig_span: &id003
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x44e8
  span: *id003
nrf_modem_lib_tx:
  address: 0x200104e8
  end_address: 0x200124e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_ctrl
  region: sram_primary
  size: 0x2000
otp:
  address: 0xff8108
  end_address: 0xff83fc
  region: otp
  size: 0x2f4
spm:
  address: 0x10200
  end_address: 0x20200
  inside:
  - mcuboot_primary_app
  placement:
    before:
    - app
  region: flash_primary
  size: 0x10000
spm_sram:
  address: 0x20000000
  end_address: 0x20010000
  inside:
  - sram_secure
  placement:
    after:
    - start
  region: sram_primary
  size: 0x10000
sram_nonsecure:
  address: 0x20010000
  end_address: 0x20040000
  orig_span: &id004
  - sram_primary
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x30000
  span: *id004
sram_primary:
  address: 0x200144e8
  end_address: 0x20040000
  region: sram_primary
  size: 0x2bb18
sram_secure:
  address: 0x20000000
  end_address: 0x20010000
  orig_span: &id005
  - spm_sram
  region: sram_primary
  size: 0x10000
  span: *id005

Changing for example empty_1 to my setting area
pm_static.yml:

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
EMPTY_1:
  address: 0xf0000
  end_address: 0xf8000
  placement:
    after:
    - mcuboot_secondary
  region: flash_primary
  size: 0x8000
settings:
  address: 0xfe000
  end_address: 0x100000
  placement:
    after:
    - littlefs_storage
  region: flash_primary
  size: 0x2000
app:
...
...
...

Should be ok?

Though Im confused about the dts definitions still.
Do I have to change them for my board?
The generated .yml and the dts dont quite add up, or is it OK to leave it as is?
 

&flash0 {

	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x00000000 0x10000>;
		};
		slot0_partition: partition@10000 {
			label = "image-0";
		};
		slot0_ns_partition: partition@50000 {
			label = "image-0-nonsecure";
		};
		slot1_partition: partition@80000 {
			label = "image-1";
		};
		slot1_ns_partition: partition@c0000 {
			label = "image-1-nonsecure";
		};
		scratch_partition: partition@f0000 {
			label = "image-scratch";
			reg = <0x000f0000 0xa000>;
		};
		storage_partition: partition@fa000 {
			label = "storage";
			reg = <0x000fa000 0x00006000>;
		};
	};
};